1. Technical Field
This disclosure relates to semiconductor substrates, semiconductor devices, and image sensors, as well as methods of fabricating semiconductor substrates, semiconductor devices, and image sensors.
2. Description of the Related Art
Image sensors are devices that convert optical images into electrical signals. Recently, with the development of the computer and communication industries, the demand for image sensors with enhanced performance is growing, as they are now used in digital cameras, camcorders, personal communication systems (PCS), game devices, surveillance cameras, micro-cameras for medical use, and robots.
In an image sensor, light output from a lens formed on a multi-wiring layer passes between wiring layers of the multi-wiring layer, and is then input to a photoelectric converter. In this structure, the multi-wiring layer attenuates the light. Therefore, the amount of light actually reaching the photoelectric converter may be insufficient. That is, since the multi-wiring layer reduces the aperture ratio of the photoelectric converter, the amount of light incident on the photoelectric converter significantly decreases, which, in turn, reduces sensitivity.
In order to solve this problem, a rear-side irradiation-type image sensor has been implemented. In the rear-side irradiation-type image sensor, light is irradiated from the rear side of a semiconductor substrate (opposite the multi-wiring layer), and a photoelectric converter receives the light. In this structure, the multi-wiring layer does not hinder the light. In addition, the effective aperture ratio of the photoelectric converter can be increased, and sensitivity can be enhanced.
In order to form the rear-side irradiation-type image sensor, the lower part of the semiconductor substrate must be removed after the photoelectric converter and the multi-wiring layer are formed on the semiconductor substrate. Here, the lower part of the semiconductor substrate must be uniformly removed close to the photoelectric converter without damaging the photoelectric converter, so that the photoelectric converter can receive uniform light. Therefore, a technology for uniformly removing the whole surface of the semiconductor substrate without damaging the photoelectric converter is needed.